U.S. patent number 4,418,358 [Application Number 06/204,883] was granted by the patent office on 1983-11-29 for method and system to correct color errors in color television signals generated by scanning a film.
This patent grant is currently assigned to Armand Belmares-Sarabia, Robert Bosch GmbH. Invention is credited to Armand Belmares-Sarabia, Dieter Poetsch.
United States Patent |
4,418,358 |
Poetsch , et al. |
November 29, 1983 |
Method and system to correct color errors in color television
signals generated by scanning a film
Abstract
In order to achieve color correction of color television signal
generated by a film scanner which includes a scanning device and a
digital frame store, correction means are arranged before and after
a frame store. Correction data are stored during a first film run
and reproduced during a second film run, e.g. when the film is
televised. The correction may be performed during motion and still
motion of the film without increasing of quantization errors.
Inventors: |
Poetsch; Dieter (Ober-Ramstadt,
DE), Belmares-Sarabia; Armand (Holbrook, NY) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DE)
Belmares-Sarabia; Armand (Holbrook, NY)
|
Family
ID: |
22759872 |
Appl.
No.: |
06/204,883 |
Filed: |
November 7, 1980 |
Current U.S.
Class: |
358/506;
348/222.1; 348/96; 348/E9.009; 358/527 |
Current CPC
Class: |
H04N
9/11 (20130101) |
Current International
Class: |
H04N
9/11 (20060101); H04N 009/535 () |
Field of
Search: |
;358/54,75-80,214,215,216,21,22 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Richardson; Robert L.
Attorney, Agent or Firm: Frishauf, Holtz, Goodman &
Woodward
Claims
We claim:
1. A Color Correction System for a television film scanner which
includes an opto-electronic scanning device (1) providing scanned
color component signals and a digital store (14) comprising
first signal correction means (11) connected to receive the scanned
signals from said scanning device, and being connected between said
scanning device (1) and said digital store (14); and second signal
correction means (16, 17, 18) being connected to the output of the
digital store (14).
2. A System according to claim 1, comprising light control means 6
being arranged between the film and the scanning device.
3. A System according to claim 1 wherein said first (11) and second
(16, 17, 18) signal correction means comprise black and white level
control, gamma control for each individual color signal (red,
green, and blue), and master control means (22, 23) for black,
gain, and gamma, and matrix means.
4. A System according to claim 3, wherein first signal correction
means comprise black and white level control for each individual
color signal.
5. A System according to claims 3 or 4 wherein said first signal
correction means comprise basic alignment means for negative
film.
6. A System according to claim 1, wherein the output signals of the
opto-electronic scanning device are supplied to the digital store
(14) with a master gamma of about 1 and wherein said signals are
analogue-to-digital converted using at least an 11 bits linear
quantization response.
7. A System according to claim 1, including non-linear
predistortion means (12);
and wherein the output signals of said scanning device are supplied
to the digital store (14) after non-linear predistortion and an 8
bit quantization.
8. A system according to claim 7, wherein the second correction
means include distortion means with an inverse function with
respect to said predistortion means.
9. A System according to claim 7, wherein said pre-distortion means
(12) provide an amplitude distortion function according to the
standard television gamma.
10. A System according to claim 1 wherein the first correction
means includes 8-bit quantizing means (1) non-linear predistortion
means (12), and first signal control means (11) being arranged
before said digital store (14);
and the second correction means, arranged after the digital store
(14) includes a signal path for luminance signals having luminance
control means (18) and a signal path for chrominance signals having
chrominance control means (16, 17);
wherein said luminance control means (18) is arranged for
individually controlling white, black, and gamma balance.
11. A System according to claim 10, wherein said chrominance
control means comprise at least one of: linear matrix circuits;
non-linear matrix circuits.
12. A System according to claim 10, wherein said chrominance
control means (16, 17) comprise further circuits for gamma, black,
and white control of the individual color difference signals.
13. A System according to claim 1 wherein contour correction means
(28) are arranged directly coupled to the digital store (14)
and
wherein the output signal of said contour correction means is added
to the luminance signal (Y) after correction in said second signal
correction means (18).
14. A System according to claim 1 wherein the inputs of a color
television encoder (19) are connected to the outputs of said second
signal correction means (16, 17, 18).
15. A System according to claim 1, wherein the inputs of a
RGB-matrix (26) are connected to the outputs of said second signal
correction means (16, 17, 18).
16. A System according to claim 1 comprising contour correction
means (28) the output signal of which is adjustable as a function
of a control signal and storage means (27) for storing said control
signal.
17. Method of correcting color errors in color television signals
generated by scanning a film by a film scanner with a digital frame
store, comprising the steps of
during a first film run, generating video signals by a film
scanning means (1), displaying the signals on a color television
monitor and generating correcting signals, and writing the
generated corrected signals into a frame store (14) after having
been corrected,
storing first correction data and data indicating the film
position,
reading-out the frame store (14) and correcting the signals being
read out from the frame store (14),
storing second correction data,
scanning the film once more to provide a second film run, and
during the second film run retrieving the stored first and second
correction data according to the actual film position with respect
to the scanning means (1) and correcting the signals being written
in the frame store (14) as well as the signals being read out of
the frame store according to the stored respective first and second
correction data.
18. Method according to claim 17, wherein during the first film run
one or more film frames are scanned repeatedly.
19. Method of correcting color errors in color television signals
generated by scanning a film by a film scanner with a digital frame
store, comprising the steps of:
during a first film run displaying the signals on a color
television monitor,
correcting the signals being read-out of the digital frame store
(35) in order to reduce color errors,
storing the data of said correction,
during a second film run applying said data to correction means,
which influence the signals to be written into the digital frame
store (35).
20. Color correction system for a television film scanner which
includes an opto-electronic scanning device (1) and a digital frame
store (35) comprising signal correction means (31, 32) being
alternatively switchable (36, 37) into the signal path between the
scanning device (1) and the frame store (35) or into the signal
path between the frame store (35) and an output terminal (38) of
the signal, control means (39, 40; 42) to control the color
correction means by control signals, and storage means (41) to
store said control signals.
Description
The invention relates to a system for modifying the color
characteristics of video signals produced from film by a television
film scanner.
BACKGROUND OF THE INVENTION
Color films are frequently of different color quality, and
variations may even occur during a single film. Thus it is
necessary to provide color television film scanners with color
correction systems. According to systems well known in the art
first of all the color films are observed and according to the
visual impression thus obtained the transmission characteristics of
the transmission means connected in the paths of the signals are
adjusted to cause a reduction in the color errors. Simultaneously
these correction factors are stored upon an information carrier.
Later, when the films are played back, the correction factors are
reproduced from the information carrier and are delivered to the
transmission means in such a manner that the transmission
characteristics thereof are influenced to cause a reduction in the
color errors.
These systems are normally connected to the outputs of the film
scanners, like so-called flying-spot-film scanners or film scanners
including pick-up tubes.
SUMMARY OF THE INVENTION
The purpose of the present invention is to offer a color correction
system which is adapted to a film scanner comprising a digital
frame store.
It is an object of the invention to prevent enlargement of
quantization errors which are unavoidable by using digital stores,
due to extreme non-linear corrections which might be necessary in
order to correct gamma errors of the film, especially negative
film; or due to over-proportional amplification of one or more
component signal (e.g. B-Y).
It is another object of the invention to correct color errors while
the film is not in continuous motion. This provides an operator
with enough time to make corrections in an optimum manner at the
commencement of each scene.
Briefly, in accordance with the invention, first signal correction
means are arranged between a scanning device and the digital store
and second signal correction means are connected to the output of
the digital store, correction data provided during a first or
preview run of the film being stored together with film position
information, and retrieved and applied to the scanning signals
during a second, or display run, e.g. when the film is being
televised.
DESCRIPTION OF THE DRAWINGS
The invention will now be explained in more details with reference
to the figures of the accompanying drawings therein.
FIG. 1 is a schematic block diagram of a first embodiment of the
invention, and
FIG. 2 shows a schematic block diagram of a second embodiment of
the invention.
In FIG. 1, reference 1 indicates a film scanning device such as a
CCD (charged coupled device) including all circuits to operate this
device, e.g. pre-amplifiers. In a known film scanner this device
comprises 3 CCDs, one for each color component. The light from a
light source 2 passes through a condensor lense 3, the film 4, an
objective lense 5, and a neutral density filter 6 to the scanning
device 1.
The film 4 is transported by a capstan 7; a well-known indicator 8
indicates the film position. Other parts of the film scanners are
well-known and are not shown in FIG. 1 since the explanation of
such parts is not necessary for the understanding of the invention.
The color component signals RGB are supplied to first signal
correction means 11 then to non-linear pre-distortion means 12 and
after being converted to digital signals by means of an
analogue-to-digital converter 13 written in the store 14. The store
14 is a digital store having a capacity of at least one TV frame.
By means of a digital-to-analogue converter 15, the output signals
of the store 14 are converted into analogue signals and supplied
via second signal correction means 16,17,18 to the encoder 19. At
the output of the encoder 19, a composite color video signal (CCVS)
is available. The signals R-Y, B-Y, and Y are also supplied to a
matrix 26 to produce color component signals R, G, and B.
The operation of the film scanner is controllable by remote-control
means 21. While the film 4 is moving, the film is scanned line by
line by the scanning device 1. The output signals of the scanning
device 1 do not conform with the television standard especially
with respect to interlacing and line frequency. By an appropriate
control of the write and read process of the store 14, signals are
generated which comply with a television standard e.g. the NTSC
standard.
Details thereof are described in the U.S. patent application Ser.
No. 928,783, now U.S. Pat. Nos. 4,288,818, Sept. 8, 1981 and
4,312,017, Jan. 19, 1982, Poetsch.
In digital video systems 8 bit coding is commonly used. This is a
compromise between the requirements of minimum quantization errors
and of economical construction of digital stores and of
analogue-to-digital and, respectively, digital-to-analogue
converters. Such 8 bit coding is used in the known CCD film
scanner. Upon connection of the well-known color correction systems
with the output of such a film scanner, quantization errors which
are invisible when transmitting the output signals without any
amplitude distortion become visible by amplifying the amplitude of
one or more output signals during the color correction process.
With respect to these errors, color correction would be preferable
before the analogue-to-digital conversion.
However, the scanning device 1 generates only output signals when
the film is moving. Therefore, the setting of the color correction
by controlling the output signals of the scanning device 1 is not
possible during still, or stopped motion operation mode. To permit
the operator in order to perform corrections as carefully as
possible it may be necessary to correct a single frame. To obtain
the advantage of both possibilities, i.e. to correct a running film
or a single frame, the system according to the embodiment of the
invention of FIG. 1 comprises signal correction means before and
after the store. The signal correction means 11 which are arranged
between the scanning device and the normal gamma predistortion
circuit 12 provides coarse correction of the color errors. The
circuit 12 compensates for the non-linear response of the picture
tube of the television receivers. The remaining color errors which
do not require a substantial stretching of the amplitude response
are corrected by second correction means 16, 17, and 18 in the
paths of the signals being read out of the store 14. Another
correction which of course is to be done before the store is the
setting of the neutral density filter 6 which is remote controlled
by a motor 25 from the remote control panel 22.
The signal correction means 11,16,17, and 18 are remote
controllable by the control panels 22 and 23.
The control panel 22 comprises controls for the white and black
level of the color component signals R, G, and B and a control for
the neutral density filter. These controls enable a coarse
correction which is primarily necessary for negative films but can
also be applied with positive films. Since the correction
requirements of a negative film deviate from those of positive
film, the control panel 22 comprises pre-adjustment and storage
means for average correction values of negative film.
The second signal correction means comprise luminance, or Y
correction means 18 and chrominance matching correction means 16
and 17. The luminance correction means 18 provide for correction of
gamma, black, and white of the luminance signal Y and are
remote-controllable by means of the control panel 23.
In addition of this the color difference signals R-Y and B-Y are
supplied to the luminance correction means in order to change the
luminance matrixing formula which normally is
In the chrominance path two chrominance correction circuits are
arranged. The first one 16 allows individual matching and control
of gamma, black, and white of the color difference signals, the
second one 17 comprises essentially a non-linear matrix which
enables the separate correction of different colors. The
chrominance correction means are remote-controllable by the control
panel 23 having for each such color one joy-stick.
In order to enhance the contours of pictures reproduced by such
film scanner, a contour corrector 28 is provided for. Since the
vertical contour correction requires a comparison between the
amplitudes of the luminance signals of three adjacent lines the
contour enhancer is directly connected to the store 14. The output
of the contour enhancer 28 is connected to the input of a second
digital-to-analogue converter 29 the output signal of which is
added to the luminance signal by means of an adder 30 after the
luminance signal has been corrected.
Operation
During a first or preview run of the film 8, the controls are
adjusted scene by scene or if necessary frame by frame, adjustment
of the controls is in the sense of a reduction in the color errors.
The setting of this adjustment of the controls is stored in the
form of data in the storage means 27, e.g. punched tape or floppy
discs as used in the known color correction systems.
During a second run of the film for television purpose, the
correction information data stored in the storage means 27
retrieved. The film is then run a second time. During the second
run of the film, for television display purpose, 8 and supplied to
the first and second signal correction means 11,16,17, and 18. thus
the output signal of the system according to FIG. 1 is
automatically color corrected.
Within the scope of the invention, the second signal correction
means can be realized by digital signal processing means, e.g.
multiplying circuits and can be arranged between the frame store 14
and the D/A-converter 15.
The neutral density filter may be operated automatically by
deriving a control signal from the output signals of the scanning
device; alternatively, the amplitude of the signal can be
electronically automatically adjusted by an automatic gain control,
as it is well known in the art. In this case the position of the
neutral density filter may be stored automatically together with
the manually adjusted correction data.
Since the effect of the corrections applied to the signals before
the store can be observed only while the film is moving, in some
cases for example at normal preview speed the duration of one scene
may be too short to perform even a coarse correction. Therefore,
the film may be moved or reciprocated forwardly and backwardly
repeatedly by one or more frames for the time required for the
correction of the signals before storage of the signals for the
frame store is effected.
Film position indicator 8 is, for example, a sensor responding to
the film sprocket holes coupled to a counter, counting holes from a
reference position. The first and second signal correction means
11, and 16, 17, 18, respectively, comprise black and white level
control, gamma control for each individual color signal (red, R;
green, G; and blue, B) and master control means 22, 23 for black,
gain, and gamma (Y) and the matrix 17. The first signal correction
means 11 corrects black and white level control for each individual
color signal. Additionally, it can include basic alignment for
negative film. The output signal of the opto-electronic scanner 1
is supplied to the digital store 14 with a master gamma of about 1.
The signals are A/D converted in converter 13 and utilize at least
an 11-bit linear quantization response. The non-linear
predistortion device 12 supplies the output signal from the
scanning device to the digital store 14 after non-linear
predistortion and an 8-bit quantization. The section correction
means include distortion means with an inverse function with
respect to the predistortion. The predistortion device 12 provides
an amplitude distortion function according to standard television
gamma.
FIG. 2 shows a second embodiment of the invention. The scanning
device 1, the film 4, and the capstan device 7 are similar to those
of FIG. 1.
The store 35 comprises a frame store and associated equipment like
D/A- and A/D-converters. The first correction means are equal to
the second correction means and have similar functions as the
correction means shown in FIG. 1.
The delay devices 33 and 34 have the same delay time as the
correction means 31 and 32. The control panels 39 and 40 and the
storage means 41 are basically equal to the panels 21, 22, and 23
and the storage means 27 of FIG. 1.
During a first run of the film 4, the switches 36, 37, and 42 are
in the position shown in FIG. 2. Only the second correction means
are effective. The output signals are displayed by connecting a
color TV monitor to the output 38. Color errors are corrected by
operating the controls of the panel 40. If an extended adjustment
is necessary, the film can be stopped and the correction of the
output signals of the store 35 can be done as long as
necessary.
During a second film run the switches 36, 37, and 42 are changed
over to the not-shown position. The second correction means are
disconnected. Only the first correction means are effective.
Correction data are read out of the storage means 41
correspondingly to the film movement and control the first
correction means in the same way as the second correction means
were controlled during the first run.
In view of quantization errors this correction method is
satisfactory since disturbing quantization errors may occur only
during the first run when the signals are observed for correction
purposes but not transmitted.
Besides the color correction a control of the degree of contour
enhancement can be done during the first film run. Therefor the
contour enhancer 28 (FIG. 1) receives a control signal from the
control panel 23. This control signal can be stored together with
the color correction data and reproduced during the second film run
according to the film movement.
Color correction of television scenes reproduced from film is
described in U.S. Pat. No. 4,096,523, Belmares Sarabia et al. and
also in U.S. Pat. No. 3,610,815 describing the system known as
"Chromaloc".TM., to the disclosures of which reference is made.
* * * * *